Synthesis and characterization of 2-mono- And 1,2-diaminocarba- closododecaborates M[1-R-2-H2N-doso-CB11H10] (R = H, Ph, H2N, CyHN)

Abstract

The first primary 2-aminocarba-closo-dodecaborates [1-R-2-H 2N-Closo-CB11H10]- (R = H (1), Ph (2)) have been synthesized by insertion reactions of (Me3Si) 2NBCl2 into the trianions [7-R-7-nido-CB 10H10]3-. The difunctionalized species [1,2-(H2N)2-closo-CB11H10] (3) and 1-CyHN-2-H3N-closo-CB11H10 (H-4) have been prepared analogously from (Me3Si)2NBCl2 and 7-H3N-7-nido-CB10H12. In addition, the preparation of [Et4N] [1-H2N-2-Phcloso-CB 11H10] ([Et4N]-5) starting from PhBCl 2 and 7-H3N-7-nido-CB10H12 is described. Methylation of the [1-Ph-2-H2N-Closo-CB11H 10]- ion (2) to produce 1-Ph-2-Me3N-closo- CB11H10 (6) is reported. The crystal structures of [Et4N]-2, [Et4N]-5, and 6 were determined and the geometric parameters were compared to theoretical values derived from DFT and ab initio calculations. All new compounds were studied by NMR, IR, and Raman spectroscopy, MALDI mass spectrometry, and elemental analysis. The discussion of the experimental NMR chemical shifts and of selected vibrational band positions is supported by theoretical data. The thermal properties were investigated by differential scanning calorimetry (DSC). The pKa values of 2-H 3N-closo-CB11H11 (H-1), 1-H3N-closo- CB11H10 (H-7), and 1,2-(H3N) 2-closo-CB11H10 (H2-3) were determined by Potentiometric titration and by NMR studies. The experimental results are compared to theoretical data (DFT and ab initio). The basicities of the aminocarba-closo-dodecaborates agree well with the spectroscopic and structural properties. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.